The invention relates to generally welding machines for joining the laminations of a stack of stator cores to form a unitary assembly, and particularly to arc welding type machines.
Several prior art patents have been found to be of interest in reviewing machines in the arc welding field.
U.S. Pat. No. 4,114,019, of Sandor, Sept. 12, 1978, discloses a machine which utilizes a moving welding head which is moved relative to laminations of core-plated silicon steel. The essence of the invention is that operating current is limited to about 170 amps, and the arc welding microwire is held to a diameter of no greater than 0.050 inches, so that a weld bead which remains in molten form for only a few seconds will not trap the gaseous portions of the melted core plate and result in a porous weld.
U.S. Pat. No. 4,056,705, of Linam et al, Nov. 1, 1977, discloses a welding machine structure, wherein a plurality of welding torches are carried on a horizontal overhead beam, and a plurality of generally cylindrical workpieces are moved horizontally beneath the welding torches. The gist of the invention is to control the speed of the horizontal movement and to use scanner means on the welding guns to sequentially activate and deactivate the weld guns.
U.S. Pat. No. 4,229,642, of Sakurai et al, Oct. 21, 1980, discloses a large scale welding machine having a frame-supported, horizontally movable, truck which carries a horizontal workpiece on its central axis, and the truck is fixedly positioned, i.e., grossly positioned to descrete predetermined work stations along the track to get within welding range of the welding head. The welding head is carried on a short horizontal slide and is capable of performing a horizontal bead of weld on the workpiece.
U.S. Pat. No. 4,129,771, of Pinettes et al, Dec. 12, 1978, discloses a method for butt welding cylindrical metal rods, wherein a plurality of rods are vertically positioned above one another and butted end-to-end. A pair of rods to be welded are held between work tongs or chucks, and a welding torch is carried midway between the workholding tongs. The workpieces are rotated and a butt weld is formed at the juncture of the workpiece ends. After forming a butt weld, the workpieces are vertically moved to present the next butt ends to the welding torch. Thus, vertical movement is merely sequential to move the ends of the workpiece to the torch station following a weld operation.
U.S. Pat. 1,453,026, of Smith, Apr. 24, 1923, discloses a single electrode machine of the conventional arc welding type, which mounts the welding electrode vertically above the workpiece. The workpiece may be rotated to form a circular girth weld, or the workpiece may be (generally) longitudinally moved in front of the vertical electrode to weld a curvilinear shape on the workpiece.
The prior art machines which utilize a moving head-especially of the heliarc welding type, wherein an inert gas must be supplied to the welding zone to prevent oxidation of the weld-generally have certain drawbacks. The hoses, which supply the gas, and the wire feed spool, which feeds a wire-type electrode through the center of a welding gun, are difficult to move without causing wear on the flexing members and/or interfering with machine slide movements.
The machines which utilize horizontally-held workpieces moving beneath a vertical welding head, generally have the following drawbacks: (a) the workpiece carrying slide can become prohibitively long, thus taking up large floor space at the machine site; (b) the only effective weld which can be laid down on the workpiece is the weld on top of the work because it is very difficult to weld from underneath the workpiece and maintain the bead form. Thus, such machines are generally restricted to effectively using only one welding head.
Applicant has determined that the most effective type of machine for consistent quality control of weld, and for ease of machine movements and maintenance of welding head components, is that of a structure which supports the workpiece in a vertical attitude and moves the workpiece past a stationary heliarc welding head. A plurality of welding heads may be positioned radially around a workpiece and the welding heads may thereby simultaneous weld beads of identical quality.
Applicant's inventive structure has therefore obviated the difficulties inherent in the prior art devices.